This invention relates generally to a sectional garage door, and more specifically, to a solution for assisting movement of uneven section weight distribution in garage doors between open and closed positions.
Garage doors are typically made up of several sections that are attached together by hinges. A problem in the garage door industry is uneven section weight distribution, which typically occurs when one section in a garage door is much heavier than other sections. Uneven weight distribution may be caused, for example, by the addition of windows, extra strutting, etc., in some of the section and may create balancing challenges to a garage door as the heavy section transitions from its vertical orientation to horizontal or vice versa as the door opens and closes.
Historically, upward acting sectional doors have been provided with counterbalance mechanisms comprising, typically, a torsion coil spring or extension spring operably engaged with the door. These mechanisms, however, do not adequately account for the movement of dissimilarly weighted sections of the door.
U.S. Patent Application Publication No. 2011/0220304 to Diaz teaches a counterbalance system which attempts to address this problem and discloses an elongated shaft supported for rotation between support brackets located above the door opening. Torsion coil counterbalance springs are sleeved over the shaft, and at least one cylindrical tubular sleeve is disposed over the shaft and within each of the springs. When the springs are wound to provide for exerting a torque on the shaft, the inside diameters of the coils are reduced and a number of coils become forcibly engaged with the sleeve, while other coils remain free to contract or expand. In this manner, the effective torque or force exerted by the spring is modified from that of a conventional torsion coil spring. However, the system according to the Diaz publication would require complete replacement of the counterbalance system to retrofit an existing door installation in an attempt to address this problem.
U.S. Pat. No. 8,162,026 to Lundahl also discloses a system to address the problem of unevenly weighted sectional doors including a horizontal rotating shaft mounted above the door opening, and primary and auxiliary torsion springs sleeved over the shaft. The primary torsion spring provides a lifting force for the door throughout its travel path while opening and provides a weight support force for the door throughout its travel path while closing. The auxiliary torsion spring provides a lifting force for the door only during a portion (e.g., during travel of the door over an initial segment, such as approximately the first three feet) of its travel path while opening and provides a weight supporting force for the door only during a portion (e.g., during travel of the door over a final segment, such as the last three feet) of its travel path while closing. Lundahl teaches another modification of a traditional counterbalance torsion spring system and, as such, offers a costly and complex attempt to solve the problem of unevenly weighted sectional doors.